Voltage splitting off of an SMPS.

Discussion in 'The Projects Forum' started by frascati, Mar 5, 2013.

  1. frascati

    Thread Starter Member

    Jun 1, 2010
    28
    0
    I need to supply a device with 9vdc, 15vdc, and 19.5vdc. I have a 19.5vdc 5.13 amp switch mode power supply.

    [​IMG]

    The amperage is more than enough for all requirements.

    Is this a simple circuit to make? My electronics skills are rudimentary. But If it involves some series of resistors or other basic components I can follow directions quite well.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    What's the current requirement for each voltage?
     
  3. frascati

    Thread Starter Member

    Jun 1, 2010
    28
    0
    That's not an easy one, for me. Fairly confident that the 5.13 is sufficient, but all I could do is experiment. Unless I could actually fry something?

    Here's the CD/AM/FM I"m working with. It's just a Sony clone of the Bose Wave with two main speakers and a rear "sub" woofer.
    [​IMG]

    Grainy, but all I had.

    Here are a couple pages of the basic specs from the internet
    http://usdn3.nodevice.com/preview/big/160/160690-1.jpg
    http://usdn3.nodevice.com/preview/big/160/160690-2.jpg

    I've turned it into a fun little project to upgrade the speakers and add a better amplifier.
    Here's the Amp
    [​IMG]

    And the page I purchased it from....
    http://www.ebay.com/itm/Finished-bo...mplifier-board-subwoofer-output-/251210310744
    It's 10x the sound quality of the existing amp in the Sony.

    And I purchased replacement speakers equally superior and sized to "drop in".

    I'm controlling the amp above right off of the preamp board in the Sony
    [​IMG]
    [​IMG]
    ...tapping into the main volume pins on the bottom side.

    As to the current requirements. The amplifier vendor provides nothing specific on this, but suggests a 15 to 20vdc SMPS to drive the amp. SMPS sold online for this size chip amp are commonly 2.0 amps.
    I know how to measure current draw for a known input (120vac) using a DMM, but unfortunately the radio is completely disassembled right now so I cannot get in between the linear transformer onboard while it's running to check for current. It don't think it's exceeding 3 amps though.

    Here is the onboard linear xformer.
    [​IMG]
    [​IMG]

    I could just leave this be. But then I'd have to keep the 120 cord connected and try to mount the SMPS in the radio. No room for that.
    So the next option is to just remove it, plug the SMPS into the wall, connect to the radio with the single 19.5vdc cord. The OEM xformer has 9 and 15vdc clearly marked outputs. I can connect directly to my new amplifier with 19.5vdc and then feed the 9 and 15 volt and ground wires leading out of the old xformer.
     
  4. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    Sidenote:

    The Bose Wave doesn't have a subwoofer (The Wave Pro does). I was suprised to see there's only 2 little 3" speakers in a big plastic folded horn enclosure inside the unit.

    There really isn't anything inside them (besides the Bose logo) to put such a premium on them, though they do have nice transformer.
     
  5. crutschow

    Expert

    Mar 14, 2008
    13,052
    3,244
    I suspect Bose has the highest profit margin of any sound system manufacturer in the business. Such is the power of advertising.

    Edit: You could likely use a linear regulator, such as the LM317, to derive the lower voltages, but without knowing the current requirements I can't say for sure.
     
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